From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C0422C43331 for ; Fri, 6 Sep 2019 16:09:03 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9189A2070C for ; Fri, 6 Sep 2019 16:09:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9189A2070C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:58086 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i6GnG-0000oX-8L for qemu-devel@archiver.kernel.org; Fri, 06 Sep 2019 12:09:02 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52251) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i6GjN-0005FC-Fm for qemu-devel@nongnu.org; Fri, 06 Sep 2019 12:05:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i6GjK-0000aj-UW for qemu-devel@nongnu.org; Fri, 06 Sep 2019 12:05:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35670) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i6GjK-0000Zp-N0 for qemu-devel@nongnu.org; Fri, 06 Sep 2019 12:04:58 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 59CCA30821AE; Fri, 6 Sep 2019 16:04:57 +0000 (UTC) Received: from [10.3.116.234] (ovpn-116-234.phx2.redhat.com [10.3.116.234]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E9B073DA6; Fri, 6 Sep 2019 16:04:52 +0000 (UTC) To: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , Tony Nguyen , qemu-devel@nongnu.org References: <20190902012647.1761-1-tony.nguyen@bt.com> <41e61c1c-15b0-d028-fc23-52e2c59319d2@redhat.com> <93172f42-7506-65d0-5754-248c3fc31aa1@redhat.com> <867bdb4b-3eef-0660-6db2-a2e6a0ab5a0e@redhat.com> From: Eric Blake Openpgp: preference=signencrypt Autocrypt: addr=eblake@redhat.com; keydata= xsBNBEvHyWwBCACw7DwsQIh0kAbUXyqhfiKAKOTVu6OiMGffw2w90Ggrp4bdVKmCaEXlrVLU xphBM8mb+wsFkU+pq9YR621WXo9REYVIl0FxKeQo9dyQBZ/XvmUMka4NOmHtFg74nvkpJFCD TUNzmqfcjdKhfFV0d7P/ixKQeZr2WP1xMcjmAQY5YvQ2lUoHP43m8TtpB1LkjyYBCodd+LkV GmCx2Bop1LSblbvbrOm2bKpZdBPjncRNob73eTpIXEutvEaHH72LzpzksfcKM+M18cyRH+nP sAd98xIbVjm3Jm4k4d5oQyE2HwOur+trk2EcxTgdp17QapuWPwMfhaNq3runaX7x34zhABEB AAHNHkVyaWMgQmxha2UgPGVibGFrZUByZWRoYXQuY29tPsLAegQTAQgAJAIbAwULCQgHAwUV CgkICwUWAgMBAAIeAQIXgAUCS8fL9QIZAQAKCRCnoWtKJSdDahBHCACbl/5FGkUqJ89GAjeX RjpAeJtdKhujir0iS4CMSIng7fCiGZ0fNJCpL5RpViSo03Q7l37ss+No+dJI8KtAp6ID+PMz wTJe5Egtv/KGUKSDvOLYJ9WIIbftEObekP+GBpWP2+KbpADsc7EsNd70sYxExD3liwVJYqLc Rw7so1PEIFp+Ni9A1DrBR5NaJBnno2PHzHPTS9nmZVYm/4I32qkLXOcdX0XElO8VPDoVobG6 gELf4v/vIImdmxLh/w5WctUpBhWWIfQDvSOW2VZDOihm7pzhQodr3QP/GDLfpK6wI7exeu3P pfPtqwa06s1pae3ad13mZGzkBdNKs1HEm8x6zsBNBEvHyWwBCADGkMFzFjmmyqAEn5D+Mt4P zPdO8NatsDw8Qit3Rmzu+kUygxyYbz52ZO40WUu7EgQ5kDTOeRPnTOd7awWDQcl1gGBXgrkR pAlQ0l0ReO57Q0eglFydLMi5bkwYhfY+TwDPMh3aOP5qBXkm4qIYSsxb8A+i00P72AqFb9Q7 3weG/flxSPApLYQE5qWGSXjOkXJv42NGS6o6gd4RmD6Ap5e8ACo1lSMPfTpGzXlt4aRkBfvb NCfNsQikLZzFYDLbQgKBA33BDeV6vNJ9Cj0SgEGOkYyed4I6AbU0kIy1hHAm1r6+sAnEdIKj cHi3xWH/UPrZW5flM8Kqo14OTDkI9EtlABEBAAHCwF8EGAEIAAkFAkvHyWwCGwwACgkQp6Fr SiUnQ2q03wgAmRFGDeXzc58NX0NrDijUu0zx3Lns/qZ9VrkSWbNZBFjpWKaeL1fdVeE4TDGm I5mRRIsStjQzc2R9b+2VBUhlAqY1nAiBDv0Qnt+9cLiuEICeUwlyl42YdwpmY0ELcy5+u6wz mK/jxrYOpzXKDwLq5k4X+hmGuSNWWAN3gHiJqmJZPkhFPUIozZUCeEc76pS/IUN72NfprZmF Dp6/QDjDFtfS39bHSWXKVZUbqaMPqlj/z6Ugk027/3GUjHHr8WkeL1ezWepYDY7WSoXwfoAL 2UXYsMAr/uUncSKlfjvArhsej0S4zbqim2ZY6S8aRWw94J3bSvJR+Nwbs34GPTD4Pg== Organization: Red Hat, Inc. Message-ID: Date: Fri, 6 Sep 2019 11:04:52 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Fri, 06 Sep 2019 16:04:57 +0000 (UTC) Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH] memory: Set notdirty_mem_ops validator X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 9/6/19 8:44 AM, Eric Blake wrote: > On 9/6/19 8:24 AM, Philippe Mathieu-Daud=C3=A9 wrote: >=20 >>>>> static const MemoryRegionOps notdirty_mem_ops =3D { >>>>> .write =3D notdirty_mem_write, >>>>> - .valid.accepts =3D notdirty_mem_accepts, >>>>> .endianness =3D DEVICE_NATIVE_ENDIAN, >>>>> .valid =3D { >>>>> .min_access_size =3D 1, >>>>> .max_access_size =3D 8, >>>>> .unaligned =3D false, >>>>> + .accepts =3D notdirty_mem_accepts, >>>> >>>> I'm surprised the compiler doesn't emit any warning... >>> >>> Same here. Actually, I just played with -Woverride-init in gcc 9.2.1 (and clang's comparable -Winitializer-overrides, which we intentionally disable during configure), and they come pretty close - both compilers DO flag when an implicit zero-initialization due to partial =3D{} overrides an earlier initialization. But sadly, they also warn when one specific init of a smaller subobject overrides another earlier specific init of a larger subobject such as an array range operator. So qobject/json-lexer.c and others fail to compile under the existing warning option, which is why we disable it during configure (clang has it as part of -Wall; gcc only has it as part of -Wextra which we do not use). In researching further, I see: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D24010#c4 which explains why -Woverride-init is NOT part of gcc's -Wall, precisely because of our range pre-initialization usage. So I filed: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D91688 seeing if the gcc devs would consider splitting into -Woverride-init=3D[12], where 1 only flags a larger subobject overriding an earlier smaller one (would have caught our bug) and 2 flags an equal-size or smaller subobject overriding an earlier large one (which we would not use, because we rely on that for range pre-initialization). --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org